As a thin, lightweight, display device capable of high-quality image display with low power consumption, a liquid crystal display device including TFTs (Thin Film Transistors) has been used in a wide range of applications, including a personal computer, a mobile telephone, and a television set. Such a liquid crystal display device is constituted by an array substrate on which TFT elements are disposed, a counter substrate on which counter electrodes are disposed, and liquid crystal which is contained in between the array substrate and the counter substrate. In recent years, various kinds of liquid crystal display devices that realize improvement in image quality and reduction in power consumption have been proposed.
For example, the liquid crystal display device disclosed in Patent document 1 has a short circuit and serially performs writing to pixels while making adjacent signal lines short-circuited by the short circuit. With this arrangement, an electric potential of each signal line immediately before writing operation becomes an intermediate potential to which electric potentials of a positive-polarity signal and a negative-polarity signal are leveled, so that power consumption of a signal line drive circuit is reduced by half.
The liquid crystal device disclosed in Patent document 2 supplies data signals whose polarities are opposite to each other respectively to adjacent data signal lines, and makes the adjacent data signal lines short-circuited. This causes the data signal lines to converge on an intermediate potential (pre-charge potential). A load at the pre-charging is only a load of a short circuit between the data signal lines. This decreases a parasitic resistance and a parasitic capacitance and thus enables pre-charging at a high speed.
The display device disclosed in Patent document 3 has electrical charge collecting means that is controlled to make at least two output terminals short-circuited for a predetermined period every n (n is an integer not less than 2) horizontal scanning periods. The display device collects electrical charges at the time of polarity change of the output terminals so that electrical charges are reallocated via the electrical charge collecting means. This realizes improvement in display quality and reduction in power consumption.
The display device disclosed in Patent document 4 has a grayscale voltage generating circuit which supplies a plurality of voltages (first voltages) that is higher than a predetermined potential and another plurality of voltages (second voltages) that is higher than the predetermined potential, and makes odd-numbered lines of source lines and even-numbered lines of the source lines short-circuited by switching between the first voltage and the second voltage at predetermined intervals. This effectively reduces power consumption.
The liquid crystal display device disclosed in Patent document 5 separates digital/analogue converting means and output terminals by means of a separation switch in a blanking period, and makes the output terminals short-circuited by shorting means. This reduces power consumption at the reversal of a drive signal.
The drive circuit disclosed in Patent document 6 separates outputs of a source line driving section from source lines at the initial stage of writing to liquid crystal capacity, and makes the source lines short-circuited at a predetermined potential. This reduces current consumption and shortens the length of time the source lines are charged/discharged to a predetermined level.
In impulse-type display devices such as CRTs (Cathode Ray Tubes), a turn-on period in which an image is displayed and a turn-off period in which no image is displayed are alternated in each pixel. In the case of moving images, for example, human eyes do not perceive afterimage of an object because a turn-off period is provided each time an image for one screen is updated. Because of this, a background and an object are clearly distinguished and a moving image is perceived without discomfort.
On the other hand, Patent documents 1 through 6 give rise to the following problem. That is, in hold-type display devices such as liquid crystal display devices including TFTs (Thin Film Transistors), the luminance of each pixel is determined by a voltage held by each pixel capacity, and the voltage held by the pixel capacity is maintained for one frame period after update. As such, in a hold-type display device, a voltage held as pixel data by a pixel capacity is maintained until the next update. Therefore an image of each frame is temporally close to the image of the directly preceding frame. This allows human eyes to perceive an afterimage of a moving object, when a moving image is displayed. As illustrated in FIG. 59, for example, in a case an image OI indicative of an object moves in A direction (pattern movement direction), an afterimage (trailing afterimage) AI appears as if the object leaves trails.
Hold-type display devices such as active matrix type liquid crystal display device involve such a trailing afterimage AI when displaying a moving image. For this reason displays such as television receivers, which predominantly display moving images, have typically been impulse-type display devices. However, because of recent strong demands for reduction in weight and thickness of displays such as television receivers, hold-type liquid crystal display devices such as liquid crystal display devices, which allow for reduction in weight and thickness, have rapidly been used as the aforesaid displays.
As such, there has been demand for non-hold-type liquid crystal display devices that is free from the trailing image AI. As such a liquid crystal display device, Patent document 7 discloses a method for realizing impulse display in a liquid crystal display device by inserting (black insertion) a black display period in each frame period, or other means.
[Patent Document 1]    Japanese Unexamined Patent Publication No. 243998/1997 (Tokukaihei 9-243998; published on Sep. 19, 1997)
[Patent Document 2]    Japanese Unexamined Patent Publication No. 85115/1999 (Tokukaihei 11-85115; published on Mar. 30, 1999)
[Patent Document 3]    Japanese Unexamined Patent Publication No. 279626/2004 (Tokukai 2004-279626; published on Oct. 7, 2004)
[Patent Document 4]    Japanese Unexamined Patent Publication No. 121911/2005 (Tokukai 2005-121911; published on May 12, 2005)
[Patent Document 5]    Japanese Unexamined Patent Publication No. 212137/1997 (Tokukaihei 9-212137; published on Aug. 15, 1997)
[Patent Document 6]    Japanese Unexamined Patent Publication No. 30975/1999 (Tokukaihei 11-30975; published on Feb. 2, 1999)
[Patent Document 7]    Japanese Unexamined Patent Publication No. 66918/2003 (Tokukai 2003-66918; published on Mar. 5, 2003)
[Patent Document 8]    Japanese Unexamined Patent Publication No. 310113/2004 (Tokukai 2004-310113; published on Nov. 4, 2004)
[Patent Document 9]    Japanese Unexamined Patent Publication No. 175057/2002 (Tokukai 2002-175057; published on Jun. 21, 2002)